package com.xxl.job.admin.core.route.strategy;

import com.xxl.job.admin.core.route.ExecutorRouter;
import com.xxl.job.core.biz.model.ReturnT;
import com.xxl.job.core.biz.model.TriggerParam;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * 单个JOB对应的每个执行器，最久为使用的优先被选举 a、LFU(Least Frequently Used)：最不经常使用，频率/次数 b(*)、LRU(Least Recently
 * Used)：最近最久未使用，时间
 * <p>
 * Created by xuxueli on 17/3/10.
 */
public class ExecutorRouteLRU extends ExecutorRouter {

  private static ConcurrentMap<Integer, LinkedHashMap<String, String>> jobLRUMap = new ConcurrentHashMap<Integer, LinkedHashMap<String, String>>();
  private static long CACHE_VALID_TIME = 0;

  public String route(int jobId, List<String> addressList) {

    // cache clear
    if (System.currentTimeMillis() > CACHE_VALID_TIME) {
      jobLRUMap.clear();
      CACHE_VALID_TIME = System.currentTimeMillis() + 1000 * 60 * 60 * 24;
    }

    // init lru
    LinkedHashMap<String, String> lruItem = jobLRUMap.get(jobId);
    if (lruItem == null) {
      /**
       * LinkedHashMap
       *      a、accessOrder：true=访问顺序排序（get/put时排序）；false=插入顺序排期；
       *      b、removeEldestEntry：新增元素时将会调用，返回true时会删除最老元素；可封装LinkedHashMap并重写该方法，比如定义最大容量，超出是返回true即可实现固定长度的LRU算法；
       */
      lruItem = new LinkedHashMap<String, String>(16, 0.75f, true);
      jobLRUMap.putIfAbsent(jobId, lruItem);
    }

    // put new
    for (String address : addressList) {
      if (!lruItem.containsKey(address)) {
        lruItem.put(address, address);
      }
    }
    // remove old
    List<String> delKeys = new ArrayList<>();
    for (String existKey : lruItem.keySet()) {
      if (!addressList.contains(existKey)) {
        delKeys.add(existKey);
      }
    }
    if (delKeys.size() > 0) {
      for (String delKey : delKeys) {
        lruItem.remove(delKey);
      }
    }

    // load
    String eldestKey = lruItem.entrySet().iterator().next().getKey();
    String eldestValue = lruItem.get(eldestKey);
    return eldestValue;
  }

  @Override
  public ReturnT<String> route(TriggerParam triggerParam, List<String> addressList) {
    String address = route(triggerParam.getJobId(), addressList);
    return new ReturnT<String>(address);
  }

}
